1592, from M.Fr. perfidie, from L. perfidia "falsehood, treachery," from perfidus "faithless," from phrase per fidem decipere "to deceive through trustingness," from per "through" + fidem, acc. of fides "faith." The adj. perfidious is attested from 1598.

So the literal translation of the original Latin phrase incorporates that aspect of trust, as well...